Clothes, for some reason or another, seldom fit as well as we would like, but it is possible to alter clothing to make it fit better. While some clothing alteration services can be done at home, at times it is best to see a professional, especially with an important garment like a bridal gown. The following are common terms used in the clothing industry.

Tailor – A person who alters clothes professionally. Unlike other professions, tailoring is still often taught by apprenticeship. A good tailor is someone with a lot of experience altering clothes.

Seam – Where two or more layers of fabric are held together by stitches. Some common seams that are usually altered is the inseam, which measures the inner leg in pants, or princess seams, which help shape a shirt to the curves of a woman's body. Adding new seams is one of the most expensive services a tailor provides.

Hem – A hem is a piece of cloth that is sewn to prevent the edge of a fabric from unraveling. This term can also refer to shortening an item, like jeans, that are too long for the wearer. Items can be hemmed for between very inexpensive.

Formal wear – Clothes that are worn to formal events such as parties, proms and weddings. For men, this usually requires wearing a suit and tie, for women it means wearing a dress. Depending on how the item is made, for example a pleated dress, it may be more costly getting it altered.

Dry clean – A store where professionals clean delicate shirts, suits and dresses as well as items you might not think of, like rugs. Some will offer same day service.

I have years of experience in the film and fashion industry. I am a dressmaker, tailor, and I do professional and quick alterations for wedding and prom gowns. I also custom make costumes from any era.

For most people, simply buying clothing 'off the rack' is enough. However, this does not always work. It is especially true with formal wear and with people who don't fit the standard sizes.
There is still some work for the tailor. In the past, most clothing was custom made. Ordinary people would handle their own basic needs and go to a tailor for more complicated and important outfits. A tailor may make custom garments from scratch. More commonly, he or she will alter existing clothing. Most alterations of are suits or dresses. Expensive shirts are also commonly altered. The cost of a full custom suit can be very high.
Alterations might consist of raising or lowering a hem or adjusting a waistline. Wedding and prom dresses are commonly altered to a more exact fit. Most garment alteration shops these days are attached to dry cleaners. They also handle repairs, such as replacing the zipper on a pair of jeans. Many offer same day service at a higher cost. These shops tend, however, to handle simpler items such as minor alterations to a shirt or pair of pants.
Simple alterations are often cheaper. Of course, some people may attempt to do them themselves. This requires skill in sewing and the ability to take measurements. Community colleges often offer instruction in repairing and altering garments. In most cases, it is far easier to make a garment smaller. It is relatively easy to take in seams, but extending them involves adding extra material. Some garments, too, are not designed with seams in the appropriate place. Things can be particularly difficult for plus size individuals who often struggle to find apparel large enough.